Safety lock mechanism for momentary slide switch

ABSTRACT

A safety lock mechanism for momentary electrical switches having a spring return slide contact is adapted to maintain the switch in an off position until the lock mechanism is released, whereupon the slide contact may be moved to an on position. Upon returning the slide contact to an off position, the safety lock mechanism is adapted to automatically become engaged thereby preventing further use of the switch until the locking mechanism is again released.

United States Patent 191 Bigley et a1.

SAFETY LOCK MECHANISM FOR MOMENTARY SLIDE SWITCH Inventors: James E. Bigley, Zelienople; James E. Edgell, Bradford Woods, both of Pa Assignee: Disston, Inc., Pittsburgh/P a.

Filed: Sept. 22, 1972 App]. No.: 291,411

U.S. Cl. 200/169 R, 200/157 Int. Cl. H01h 3/20 Field of Search 200/169 R, 42 R,

References Cited UNITED STATES PATENTS 8/1970 Karpinskim 200/169 R X 8/1969 Chambers 200/157 X Oct. 16, 1973 3,457,377 7/1969 015611 200/169 R 3,379,852 4/1968 Korshak.... 200/157 3,194,084 7/1965 Filander.... 200/157 x 2,810,051 10/1957 Johnson 200/169 R Primary ExaminerRobert K. Schaefer Assistant Examiner-William J. Smith Att0rney-B. B. Olive [5 7] ABSTRACT A safety lock mechanism for momentary electrical switches having a spring return slide contact is adapted to maintain the switch in an off position until the lock mechanism is released, whereupon the slide contact may be moved to an on position. Upon returning the slide contact to an off position, the safety lock mechanism is adapted to automatically become engaged thereby preventing further use of the switch until the locking mechanism is again released.

7 Claims, 7 Drawing Figures PATENIEnum 15 am SAFETY LOCK MECHANISM FOR MOMENTARY SLIDE SWITCH BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to safety lock mechanisms adapted for use on electrical switches of the momentary type having a spring return sliding contact mechanism.

2. Description of the Prior Art The prior art in safety lock mechanisms adapted for use on electrical switches of the class described, has gerieraly provided two position manually operated locking means whereby the slide contact is prevented from being moved to an on position when the lock mechanism is in an interfering position and whereby the slide contact is able to be moved to an on position when the lock mechanism is in a non-interfering position. The type of lock mechanism must be manually set to a non-interfering position prior to use of the switch, and set to an interfering position following use of the switch to prevent further accidental use. This type of locking arrangement has found wide application in small electrical appliances and tools, particularly in those cases wherein an appliance or tool remaining unattended and in an unlocked switch position could be accidently operated, possibly causing substantial bodily injury. An example of the above type of lock mechanism in use on a cordless garden tool is shown in US. Pat. No. 3,623,223 also in pending application Ser. No. 230,341, filed Feb. 29, l972, for Convertible Cordless Electric Shrub Trimmer and Grass Shear. Due to the leverage being delivered to cutting blades in such a tool, substantial injury to fingers, for example, could result through the accidental operation of an unlocked switch.

Based on the above, there is clearly a need for a type of safety lock mechanism adapted for use on electrical switches of the momentary type having a spring return slide contact, whereby use of the switch is effectively prevented until the lock mechanism is released; and whereby the return of the slide contact to an off position automatically engages the lock mechanism thereby preventing further accidental use of the switch.

SUMMARY OF THE INVENTION The invention is directed to a safety lock mechanism for use on electrical switches of the momentary type having a spring return slide contact. The mechanism includes a latching member pivotally secured to the switch and having an abutment adapted to engage a slide button portion of the switch. The latching memlocked position until the switch slide button is moved to an on position. A guide portion in the keeper member is adapted to engage the latching member and cause it to lock when the switch slide button returns to the off position.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of the invention apparatus in operative combination with a spring return slide contact switch.

FIG. 2 is a perspective exploded view showing the relation of the switch to the invention auxiliary members.

FIG. 3 is a cutaway side view of an electric tool showing a typical application of the invention lock mechanism.

FIG. 4 is a somewhat enlarged side view of the invention lock mechanism showing the relative positions of a slide switch and an appliance or tool housing outer wall.

FIG. 5 is a top plan view of the invention lock mechanism in combination with a spring return slide switch in an off mode of operation showing the lock mechanism in a locking position.

FIG. 6 is a top plan view of the invention lock mechanism in combination with a spring return slide switch in an off mode of operation, showing the lock mechanism in an unlocked position.

FIG. 7 is a top plan view of the invention lock mechanism in combination with a spring return slide switch in an on mode of operation showing the lock mechanism in an unlocked position.

DESCRIPTION OF THE. PREFERRED EMBODIMENT Referring to FIG. 1, in a preferred embodiment the present invention comprises an auxiliary safety lock mechanism adapted for use with electrical switch 1 1 of the momentary contact type. A safety lock mechanism according to the invention includes an elongated auxiliary latching member 14 having a handle portion 15 on one end and projecting ridges 27, 28 at an opposite end. A medially located abutment means 38 on member 14 is adapted to engage and abut a slide button portion 21 of switch 11. An auxiliary integral keeper member- 18 is secured to slide button 21 and has a resilient arm means 13 which is adapted to urge latching member 14 into a slide button abutting position during a locking mode of operation. An integrally formed catch means 19 on member 18 is adapted to temporarily maintain latching member 14 in a slide button nonabutting position during a non-locking mode of operation. The said keeper member 18 is further adapted to cause locking member 14 to return to a slide button abutting position when slide button 21 is returned to a rearwardly defined off position.

Referring now to FIG. 2, an electric switch of the momentary type best suited to the invention includes a sliding contact 12 having an on and off position and which is spring loaded for return to an off position. An elongated slide button 21 is secured to contact 12 and extends through an aperture in a retainer plate 22 which forms an integral part of switch 11. Retainer plate 22 conventionally includes holes 23, 24 which extend through projecting tabs 25 situated at opposite ends of plate 22. These holes are normally used for anchoring switch 11 to the particular device in which the switch is being employed. Switch 11 is conventionally and preferably of the single pole, single throw type and has a spring returned normally rearward off position indicated at (FIG. 2). A suitable switch is manufactured by Stackpole Components Company of Raleigh, N.C., as Model No. SS-40-l which is the type shown in FIG. 2 or as Model No. SS-9-2 which is not shown but which is equally suited.

Referring further to FIG. 2, the auxiliary latching member 14 includes an elongated body portion having a centrally located pin 37 which is molded integrally therewith an extends in a pivotal relation through hole 23 in projecting tab 25. Auxiliary latching member 14 is thus adapted for pivotal securement to retainer plate 22. The body portion of member 14 further includes an abutment means generally designated 38 comprising a cut out portion 39 which is adapted to engage slide button 21. A forward abutting edge 40 is adapted to abut a leading surface 42 of slide button 21 during a locking mode of operation, which prevents slide button 21 from reaching a forward on position. Also included on auxiliary latching member is a rearwardly located handle portion 15 which is formed integral with a support member 34 that extends upwardly from the perpendicular to the plane of the elongated body portion of member 14 and terminates in a moded thumb plate 42. Forwardly located on member 14 are projecting ridges 16 which include a wedge shaped guide projection 27 and a rectangular block shaped retainer projection 28. In a preferred form, latching member 14 is of onepiece injection molded plastic.

The auxiliary keeper member 18, according to the preferred embodiment, comprises a relatively thin flat sheet of polymerized material such as nylon and which is formed to include an aperture 29 adapted to receive slide button 21. A narrow resilient arm 13 is also formed in member 18 and is adapted to resiliently abut the projecting retainer block 28 when auxiliary latching member 14 is laterally pivoted to a non-locking position. The action exerts pressure on retainer block 28 and urges latching member 14 toward a locking slide button engaging and abutting position. There is also formed in member 14 a resilient elbow 16 which terminates in a catch 19 which in turn is adapted to temporarily engage the wedge shaped guide projection 27 in a notch 43 formed therein. Latching member 14 is thus maintained in a non-locking position which allows slide button 21 to be manually advanced to a forward on position. Due to its securement with slide button 21, keeper member 18 is adapted to travel forwardly and rearwardly corresponding to movement of slide button 21. Upon release of slide button 21 and its subsequent spring controlled return to a rearward off position, a corner 45 of notch 43 is adapted to engage wedge shaped guide member 27 which in turn causes latching member 14 to be urged into a locking position wherein said abutting edge 40 comes into abutment with a leading surface 42 of slide button 21.

Many alternate forms of the keeper member will appear to those skilled in the art. For example, a spring bent to conform to the curvature of keeper member 18 and secured to slide button 21 would be suitable as would a slide button having molded features embodying said keeper member.

Prior to describing the operation of the safety lock mechanism of the invention in greater detail, an example of a preferred application of said mechanism is viewed as being helpful to a fuller understanding of the invention.

Referring now to FIG. 3, a typical application of the invention safety lock mechanism might be in a cordless electric hand tool such as a grass shear 50. As shown in a cutaway view, the invention safety lock mechanism is mounted in combination with a momentary type switch 11 of the class described such that slide button 21 is adapted to extend through an appropriate aperture 51 in the housing outer wall 53. In addition, thumb plate 42 is adapted to extend through a second aperture 55 in the housing outer wall 53 such that thumb plate 42 is manually operable from the outside of said housing. Appropriate means comprising a molded land or bracket 56 integral with an internal wall surface of said housing may be adapted to maintain the switch 11 and the safety lock mechanism in proper operating position adjacent the tool housing outer wall 53. Referring now to FIG. 4, in a typical installation the invention safety lock mechanism is adapted to be effectively sandwiched between the appliance or tool housing outer wall 53 and the body of the momentary switch (represented by dashed lines 11) being utilized. A molded ridge 48 extending across a portion of latching member 14 may be employed in such installations to prevent binding between the auxiliary members 14 and 18 of the invention mechanism and the housing outer wall 53 and to prevent pin 37 from being lifted from hole 23.

Reference is now made to FIG. 5 and to the preferred embodiment lock mechanism in combination with a momentary type electrical switch in a locked mode of operation. In this regard, the auxiliary latching member 14 is adapted to engage slide button 21 when button 21 is in a rearward off position by abutting a leading surface 42 of button 21 with the previously mentioned latching member abutment means 38, thereby preventing forward movement of slide button 21. Inthe de scribed locked position catch 19 is in a position engaging wedge shaped guide projection 27.

Reference is next made to FIG. 6 and an unlocked mode of operation. In this mode slide button 21 is no longer prevented from being moved forwardly, but as shown in FIG. 6 has not yet been moved. For purpose of illustration, handle portion 15 in FIG. 6 has been manually moved somewhat to the left thereby pivoting the abutment means 38 toward the right. lnso doing the resilient catch member 19 is adapted to yield slightly thus allowing wedge shaped guide projection 27 to move past corner 45 and toward the right to a point at which catch 19 is allowed to spring back and engage wedge shaped guide projection 27 in notch portion 43. Simultaneous with the just mentioned action, resilient arm 13 comes into contact with projection 28 on the rightward moving latching member 14 and begins to resiliently urge latching member 14 back into a locking position. The wedge shaped guide projection 27 is thus temporarily engaged with notch 43 and concomitantly abutment means 38 is maintained in a non-abutting relationship with slide button 21. It should be noted from the above that the switch 11 may be unlocked without simultaneously moving the slide button.

Referring now to FIG. 7 there is shown the unlocked mode of operation in combination with the forward momentary on position of the slide button 21. In this mode, slide button 21 is manually advanced to a forward on position and keeper member 18 is advanced correspondingly. Latching member 14 in this mode is no longer maintained in a non-locking position by engagement of notch 43 with guide projection 27, but rather is now maintained in a non-locking position by slide button 21 which has now been manually moved to a momentary forward on position. Upon subsequent release of slide button 21 and return of button 21 to a rearward off position, locking arm 14 remains urged toward a locking position by resilient arm 13 while button 21 returns to the locking position shown in FIG. 5. The forward abutting edge 40 of abutment means 38 is somewhat beveled thereby enabling automatic relocking of latching member 14 to proceed smoothly following the release of slide button 21. During use of the switch it has been found that when latching member 14 is in an unlocked position and it is not desired for some reason to operate the switch, a slight forward movement of slide button 21 is sufficient to cause relocking of the lock mechanism.

From the foregoing it is readily apparent that the invention safety lock mechanism provides an effective means for preventing operation of a momentary type slide switch until said lock mechanism is released. The lock mechanism will then remain in an non-locking position until the switch slide button is operated. Upon return of the switch slide button to an off position the invention safety lock mechanism is adapted to automatically relock the switch thereby eliminating the possibility of further accidental operation. Furthermore, when the button is in the off position and the latching member is being releasably held in the unlocked posi: tion by the keeper member the button can then be moved forwardly which forward motion acts both to release the latching member from being held by the keeper member and also causes one side of the button to engage the latching member to keep the latching member unlocked as shown in FIG. 7. In this regard, the dimension X (FIG. 7) should be sufficiently long so as to maintain an engagement with projection 27 and hold the latching member pivoted towards the unlocked position until button 21 has moved forwardly sufficiently to clear edge 40 as seen in FIG. 7.

What is claimed is:

1. In combination with an electrical switch of the momentary type having a slide contact movable to an on position and spring loaded to return to an off position within a housing including a mounting plate thereon, an elongated manually operable slide button secured to said slide contact and extending through an aperture in said mounting plate, an improved safety lock mechanism, comprising:

a. an auxiliary latching member pivotally mounted on said plate and including an elongated central body portion having an abutment formed therein adapted in a locking position to abut said slide button thereby to limit its forward linear movement and maintaining said switch in an off position and in a non-locking position to clear said button for forward linear movement, handle means integrally appended to said body portion for pivotal movement of said locking member and having an integral plural surfaced projection portion adapted to be engaged on one surface thereof to releasably hold said abutment in said non-locking position and to be engaged on another surface thereof to urge said abutment toward said locking position; and

b. an auxiliary keeper member mounted on and adapted to move linearly with said slide button proximate said latching member, said keeper member having one resilient portion adapted to engage said latching member projection portion and resiliently urge said latching member abutment toward said locking position upon each occasion of said button being released from the on position and having another portion adapted to temporarily engage said latching member projection portion and releasably hold said latching member and its abutment in a non-locking position with said button in an off position and being adapted such that upon each occasion of said button being released from its on position said latching member returns to a locked position requiring further pivoting and pivotal movement of said latching member to an unlocked position such that whenever said latching member releasably held in an unlocked position by said keeper member and said button is then moved forward to its on position said latching member is released from said keeper member and held in a non-locking position by slidably engaging said button.

2. The improved safety lock mechanism of claim 1 wherein said keeper member is integrally molded to said slide button.

3. The improved safety lock mechanism of claim 1 including means adapted to maintain said auxiliary latching member and said auxiliary keeper member operatively assembled against an electric tool housing outer wall.

4. The improved safety lock mechanism of claim 1 wherein said mounting plate includes a pair of holes laterally disposed at opposite ends, and wherein said latching member includes a pin molded integrally therewith and adapted to be received in one of said holes adjacent said off position adapting said latching member for pivotal movement with respect to said plate.

5. The improved safety lock mechanism of claim 4 wherein said abutment includes an abutting edge extending substantially perpendicular to the linear axis of movement of said slide button and which is adapted to abut a leading surface of said slide button when said latching member is in a locking mode of operation and which is adapted to clear said slide button leading surface when said latching member is in an non-locking mode of operation.

6. The improved safety lock mechanism of claim 1 wherein said auxiliary latching and keeper members are formed of molded plastic material.

7. In an electrical switch construction, in combination:

a. an electrical switch of the momentary type having a slide contact movable along a linear path to an on position and spring loaded to return to an off position, having a manually operated slide button secured to said slide contact and having a switch housing mounting said contact and button with an aperture through which said button extends;

. an auxiliary latching member pivotally mounted on said housing and including an elongated central body portion having an abutment formed therein adapted in a locking position to abut said slide button thereby to limit its forward linear movement and maintaining said switch in an off position and in a non-locking position to clear said button for forward linear movement, handle means integrally appended to said body portion for pivotal movement of said locking member and having an integral plural surfaced projection portion adapted to be engaged on one surface thereof to releasably hold said abutment in said non-locking position and to be engaged on another surface thereof to urge said abutment toward said locking position; and

. an auxiliary keeper member mounted on and ment in a non-locking position with said button in J an off position and being adapted such that upon each occasion of said button being released from its on position said latching member returns to a locked position requiring further pivoting and pivotal movement of said latching member to an unlocked position such that whenever said latching member releasably held in an unlocked position by said keeper member and said button is then moved forward to its on position said latching member is released from said keeper member and held in a non-locking position by slidably engaging said button. 

1. In combination with an electrical switch of the momentary type having a slide contact movable to an on position and spring loaded to return to an off position within a housing including a mounting plate thereon, an elongated manually operable slide button secured to said slide contact and extending through an aperture in said mounting plate, an improved safety lock mechanism, comprising: a. an auxiliary latching member pivotally mounted on said plate and including an elongated central body portion having an abutment formed therein adapted in a locking position to abut said slide button thereby to limit its forward linear movement and maintaining said switch in an off position and in a nonlocking position to clear said button for forward linear movement, handle means integrally appended to said body portion for pivotal movement of said locking member and having an integral plural surfaced projection portion adapted to be engaged on one surface thereof to releasably hold said abutment in said non-locking position and to be engaged on another surface thereof to urge said abutment toward said locking position; and b. an auxiliary keeper member mounted on and adapted to move linearly with said slide button proximate said latching member, said keeper member having one resilient portion adapted to engage said latching member projection portion and resiliently urge said latching member abutment toward said locking position upon each occasion of said button being released from the on position and having another portion adapted to temporarily engage said latching member projection portion and releasably hold said latching member and its abutment in a non-locking position with said button in an off position and being adapted such that upon each occasion of said button being released from its on position said latching member returns to a locked position requiring further pivoting and pivotal movement of said latching member to an unlocked position such that whenever said latching member releasably held in an unlocked position by said keeper member and said button is then moved forward to its on position said latching member is released from said keeper member and held in a non-locking position by slidably engaging said button.
 2. The improved safety lock mechanism of claim 1 wherein said keeper member is integrally molded to said slide button.
 3. The improved safety lock mechanism of claim 1 including means adapted to maintain said auxiliary latching member and said auxiliary keeper member operatively assembled against an electric tool housing outer wall.
 4. The improved safety lock mechanism of claim 1 wherein said mounting plate includes a pair of holes laterally disposed at opposite ends, and wherein said latching member includes a pin molded integrally therewith and adapted to be received in one of said holes adjacent said off position adapting said latching member for pivotal movement with respect to said plate.
 5. The improved safety lock mechanism of claim 4 wherein said abutment includes an abutting edge extending substantially perpendicular to the linear axis of movement of said slide button and which is adapted to abut a leading surface of said slide button when said latching member is in a locking mode of operation and which is adapted to clear said slide button leading surface when said latching member is in a non-locking mode of operation.
 6. The improved safety lock mechanism of claim 1 wherein said auxiliary latching and keeper members are formed of molded plastic material.
 7. In an electrical switch construction, in combination: a. an electrical switch of the momentary type having a slide contact movable along a linear path to an on posItion and spring loaded to return to an off position, having a manually operated slide button secured to said slide contact and having a switch housing mounting said contact and button with an aperture through which said button extends; b. an auxiliary latching member pivotally mounted on said housing and including an elongated central body portion having an abutment formed therein adapted in a locking position to abut said slide button thereby to limit its forward linear movement and maintaining said switch in an off position and in a non-locking position to clear said button for forward linear movement, handle means integrally appended to said body portion for pivotal movement of said locking member and having an integral plural surfaced projection portion adapted to be engaged on one surface thereof to releasably hold said abutment in said non-locking position and to be engaged on another surface thereof to urge said abutment toward said locking position; and c. an auxiliary keeper member mounted on and adapted to move linearly with said slide button proximate said latching member, said keeper member having one resilient portion adapted to engage said latching member projection portion and resiliently urge said latching member abutment toward said locking position upon each occasion of said button being released from the on position and having another portion adapted to temporarily engage said latching member projection portion and releasably hold said latching member and its abutment in a non-locking position with said button in an off position and being adapted such that upon each occasion of said button being released from its on position said latching member returns to a locked position requiring further pivoting and pivotal movement of said latching member to an unlocked position such that whenever said latching member releasably held in an unlocked position by said keeper member and said button is then moved forward to its on position said latching member is released from said keeper member and held in a non-locking position by slidably engaging said button. 